Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already indicate destructiveHint=true and readOnlyHint=false. The description adds that 'side effects: modifies fax record metadata', which aligns with the annotations and gives a minimal idea of what changes. It does not explain irreversible consequences, permission requirements, or whether the update is partial or complete.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is short and front-loads the action and target. The side-effects note is useful and placed separately. No verbose or redundant text, though a one-sentence elaboration on payload requirements would improve it.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the output schema exists and annotations cover safety, the description provides a minimally viable picture: what it updates and that it has side effects. It lacks explicit guidance on when to use it versus bulk/sibling update tools paddle and on any edge cases like required read state or comment semantics for a 3-param tool with a nested payload.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so each parameter is documented. The description names the two main updatable values (read state and comment) but does not explain the exact payload shape or the meaning of user_id beyond the schema's 'Default: self'. It adds little beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool updates a fax record's read state and/or comment, naming the specific resource and the fields modified. However, it does not explicitly contrast with sibling tools like bulk-update-faxes or update-outbox-fax, so some sibling differentiation is left to the names and schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description says it updates a fax record's metadata)Skip earlier. It does not state when to prefer this tool over bulk-update-faxes or update-outbox-fax, nor does it mention any preconditions such as user authorization. The context of the operation is implied by the tool name and fields.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.